What was found
AIRCRAFT WAS GROUNDED: PILOT REPORTS AT GATE, FUEL INDICATED 8.42/ 6.48 /8.37. DURING CLIMB AND CRUISE W/ CENTER PUMPS ON, RIGHT TANK QUANTITY CLIMBED TO 8.70, LEFT STAYED AT 8.42. ONCE CENTER PUMPS TURNED OFF, FUEL ONLY BURNS FROM LEFT TANK UNTIL AN APPROXIMATE IMBALANCE OF 600 #, (8.16 LEFT TANK) (8.70 RT. QUANTITY, TILL RIGHT QUANTITY STARTED TO GO LOWER. FUEL IMBALANCE REMAINED FOR DURATION OF FLIGHT. MAINTENANCE REMOVED AND REPLACED THE RIGHT WING FUEL TUBE IAW AMM 28-22-15-401. OPS CHECK GOOD.